An overview of connectors for printed circuit boards belonging to the conventional art shall be explained with reference to Japanese Utility Model Publication No. 3019279. As shown in FIG. 7 and FIG. 9, conventional electrical connectors for flat flexible cables are equipped with a cover (3) on the rear end upper portion of an insulated housing (1) that is rotatable in a forward and backward direction, and an engaging arm is equipped on the rear end portion of the base beam, and a series of lever arms (12) are provided on the rear end of the upper portion side of a U-shaped contact beam. An engaging portion comprising all of the engaging arms (19) of a plurality of conductive terminals (2) aligned in a row, and the engaging portion (16a, 17) of said cover mutually engage in such a manner that the cover is rotatable, and additionally, by opposing said lever arms and the rear end portion inner surface of the cover, the opening and closing of the opposing portions of the U-shaped contact beam is made possible by the rotation of the cover.
According to this structure, since the U-shaped second arm (8b) is fixed by the contact beam connecting portion and the front end portion support, the opening and closing of the opposing portions of the U-shaped contact beam is substantially done only by the lever arm of the first arm (8a) rear end. In the state wherein the cover (3) is flush on the body upper portion, and the opposing portions of each of the contact beam front ends are closed, when a FPC is inserted, said cover is opened and the first contact beam rear end is pushed downwards and said opposing portions are opened, and after insertion, the cover is closed and made flush to the initial body upper portion, and the FPC is gripped by returning said first arm to the initial state and closing the front end portions.
Among conventional structures that grip flat flexible cables (herebelow called FPC), for example, connectors that grip FPC's in various forms such as FIG. 4 of Japanese Unexamined Patent Publication No. 2002-190360, or FIG. 4 of Japanese Unexamined Patent Publication No. 2002-15826 have been suggested.
However, all of these connectors are in a form wherein the contact beams on one side gripping said FPC are affixed as the base portion, and gripping is done by elastically deforming the contact beams on the other side through an actuator. Therefore, since the FPC is gripped only by the elastic force of the contact beams of one side, if said elastic force is too strong, a strong force is required for the operating portion of the actuator, and if said elastic force is too weak, there is the disadvantage that it becomes easy for the FPC to slip out.